feat: CLI command 'feast serve' should start go-based server if flag is enabled

[tsotnet]

Signed-off-by: Tsotne Tabidze tsotne@tecton.ai

What this PR does / why we need it: Currently, if you enable go feature server by adding go_feature_retrieval: True in the feature_store.yaml config, it only affects the Python SDK (FeatureStore.get_online_features). This PR implements changes in the CLI, so that if you run feast serve in terminal and this flag is enabled, it'll start a Go-based feature server instead of the Python equivalent.

Note, that this does not start a separate Go subprocess. The initial Python process will keep running, while Go logic is dynamically linked to the same process. This allows the serving to be done natively in Go, while ODFVs can just call back to the initial Python logic to run the transformations with minimal overhead.

This PR only adds gRPC server though. In the next PR we'll add the HTTP serving capabilities as well.

I tested this PR by running feast init, adding the go_feature_retrieval flag to the YAML file and by running feast serve after materialization. Separately I opened Python notebook and run the following:

In [8]: from feast.protos.feast.types.Value_pb2 import RepeatedValue, Value
   ...: from feast.protos.feast.serving.ServingService_pb2 import GetOnlineFeaturesRequest, FeatureList
   ...: from feast.protos.feast.serving.ServingService_pb2_grpc import ServingServiceStub
   ...: import grpc
   ...:
   ...: request = GetOnlineFeaturesRequest(
   ...:     features=FeatureList(val=[
   ...:         "driver_hourly_stats:conv_rate",
   ...:         "driver_hourly_stats:acc_rate",
   ...:         "driver_hourly_stats:avg_daily_trips"
   ...:     ]),
   ...:     entities={
   ...:         "driver_id": RepeatedValue(val=[
   ...:             Value(int64_val=1001),
   ...:             Value(int64_val=1002),
   ...:             Value(int64_val=1003)
   ...:         ])
   ...:     }
   ...: )
   ...:
   ...: stub = ServingServiceStub(grpc.insecure_channel('localhost:6566'))
   ...: stub.GetOnlineFeatures(request)
Out[8]:
metadata {
  feature_names {
    val: "driver_id"
    val: "conv_rate"
    val: "acc_rate"
    val: "avg_daily_trips"
  }
}
results {
  values {
    int64_val: 1001
  }
  values {
    int64_val: 1002
  }
  values {
    int64_val: 1003
  }
  statuses: PRESENT
  statuses: PRESENT
  statuses: PRESENT
  event_timestamps {
    seconds: 1651044665
    nanos: 234880000
  }
  event_timestamps {
    seconds: 1651044665
    nanos: 234880000
  }
  event_timestamps {
    seconds: 1651044665
    nanos: 234880000
  }
}
results {
  values {
    float_val: 0.053211748600006104
  }
  values {
    float_val: 0.5894963145256042
  }
  values {
    float_val: 0.055955931544303894
  }
  statuses: PRESENT
  statuses: PRESENT
  statuses: PRESENT
  event_timestamps {
    seconds: 1651003200
  }
  event_timestamps {
    seconds: 1651003200
  }
  event_timestamps {
    seconds: 1651003200
  }
}
results {
  values {
    float_val: 0.030293632298707962
  }
  values {
    float_val: 0.21737541258335114
  }
  values {
    float_val: 0.6582370400428772
  }
  statuses: PRESENT
  statuses: PRESENT
  statuses: PRESENT
  event_timestamps {
    seconds: 1651003200
  }
  event_timestamps {
    seconds: 1651003200
  }
  event_timestamps {
    seconds: 1651003200
  }
}
results {
  values {
    int64_val: 738
  }
  values {
    int64_val: 145
  }
  values {
    int64_val: 831
  }
  statuses: PRESENT
  statuses: PRESENT
  statuses: PRESENT
  event_timestamps {
    seconds: 1651003200
  }
  event_timestamps {
    seconds: 1651003200
  }
  event_timestamps {
    seconds: 1651003200
  }
}

As you can see, the server is able to respond to the input request using protobuf I/O.

---

I also fixed 2 unrelated bugs in this PR that I came across:

1. make compile-go-lib was outdated. I needed to change the command to build_ext since the command got renamed at some point, add COMPILE_GO=True env variable to actually compile the go code, and --inplace flag to move the generated stuff to the actual source code location.
2. There was a bug with sqlite online store. When the sqlite online store type was explicitly included in feature_store.yaml file (which was the case when running feast init), Go was complaining that this type wasn't supported even though it was. I fixed the logic for this.

Which issue(s) this PR fixes:

Fixes #

[codecov-commenter]

Codecov Report

Merging #2617 (d6e98a2) into master (134dc5f) will decrease coverage by 0.05%.
The diff coverage is 58.33%.

@@            Coverage Diff             @@
##           master    #2617      +/-   ##
==========================================
- Coverage   81.65%   81.59%   -0.06%     
==========================================
  Files         161      161              
  Lines       13297    13304       +7     
==========================================
- Hits        10857    10856       -1     
- Misses       2440     2448       +8     

Flag	Coverage Δ
integrationtests	72.56% <58.33%> (-0.28%)	⬇️
unittests	59.40% <20.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...ython/feast/embedded_go/online_features_service.py	95.04% <50.00%> (-1.93%)	⬇️
sdk/python/feast/feature_store.py	89.23% <60.00%> (-0.38%)	⬇️
...ation/feature_repos/universal/data_sources/file.py	68.81% <0.00%> (-1.08%)	⬇️
.../integration/online_store/test_universal_online.py	95.18% <0.00%> (-0.69%)	⬇️

---

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[feast-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: pyalex, tsotnet

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[pyalex]

/lgtm